Open beverage containers such as cans or bottles must be treated under conditions that are as clean as possible, in order to preclude contaminating the containers with germs that would degrade the beverage's shelf life and taste. Regarding oxygen-sensitive beverages such as beer, exposure to oxygen also must be precluded during treatment, for instance during filling. It is known to treat the container in a clean room that contains the entire equipment even though this measure entails costly enclosure construction.
The German patent document DE 101 14 660 C2 discloses equipment of this kind where merely the region of the treatment site is protected by a curtain of clean gas against exposure to germs and oxygen. As regards this known design, a slot nozzle is configured at the treatment implement to annularly enclose the implement and projects a tubular gas curtain downward and in the direction of the container axis.
This design eliminates an expensive clean gas room around the equipment. However, this design also incurs the drawback that the flow direction of the gas curtain is directed from the treatment implement to the container, namely toward the container mouth. Contaminants piercing the gas curtain may thereby be forced toward the mouth and cause contamination. When a container is filled in the open, another problem arises, namely that the air expelled from the container, that most of the time is charged with germs and oxygen, will collide in opposite direction to the flowing gas curtain and be strongly perturbed by it. Accordingly, the interfering air from the container is not evacuated cleanly, but instead may be made to return on account of turbulence into the filling substance, that is back into the container and contaminate it again.
The objective of the present invention is to create equipment of the above kind and of simple design that shall be reliably secure from contamination.